US10141734B2 - Electrical safety device miswire detection - Google Patents
Electrical safety device miswire detection Download PDFInfo
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- US10141734B2 US10141734B2 US14/850,271 US201514850271A US10141734B2 US 10141734 B2 US10141734 B2 US 10141734B2 US 201514850271 A US201514850271 A US 201514850271A US 10141734 B2 US10141734 B2 US 10141734B2
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/44—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to the rate of change of electrical quantities
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/165—Indicating that current or voltage is either above or below a predetermined value or within or outside a predetermined range of values
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H83/00—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current
- H01H83/02—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents
- H01H83/04—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents with testing means for indicating the ability of the switch or relay to function properly
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H83/00—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current
- H01H83/14—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by imbalance of two or more currents or voltages, e.g. for differential protection
- H01H83/144—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by imbalance of two or more currents or voltages, e.g. for differential protection with differential transformer
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/26—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents
- H02H3/32—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors
- H02H3/33—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers
- H02H3/334—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers with means to produce an artificial unbalance for other protection or monitoring reasons or remote control
- H02H3/335—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to difference between voltages or between currents; responsive to phase angle between voltages or between currents involving comparison of the voltage or current values at corresponding points in different conductors of a single system, e.g. of currents in go and return conductors using summation current transformers with means to produce an artificial unbalance for other protection or monitoring reasons or remote control the main function being self testing of the device
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H83/00—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current
- H01H83/02—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents
- H01H83/04—Protective switches, e.g. circuit-breaking switches, or protective relays operated by abnormal electrical conditions otherwise than solely by excess current operated by earth fault currents with testing means for indicating the ability of the switch or relay to function properly
- H01H2083/045—Auxiliary switch opening testing circuit in synchronism with the main circuit
Definitions
- aspects of the present disclosure relate generally to electrical circuits and, more specifically, to miswire detection for electrical safety devices.
- GFCIs ground fault circuit interrupters
- a GFCI is implemented within an electrical power receptacle and performs its function by disconnecting power at a receptacle connection pair of the receptacle in response to detecting small differences in current at the receptacle carried over a live or “hot” current path and a neutral current path that may be indicative of a “ground fault,” in which at least some current is inadvertently being directed to ground from the live or neutral current path.
- detection is performed using a current transformer through which the live and neutral paths are routed within the GFCI.
- the GFCI may also provide power to one or more additional receptacles on the same electrical power circuit.
- a GFCI receptacle typically provides a line connection pair for live and neutral wires received from a circuit breaker of an electrical panel, and also provides a load connection pair for live and neutral wires for one or more additional receptacles of the same electrical power circuit, in addition to the receptacle connection pair, so that the GFCI may disconnect both the receptacle connection pair and the load connection pair from the line connection pair.
- miswiring of the GFCI in which the live and neutral wires from the circuit breaker panel are mistakenly coupled to the live and neutral lines of the load connection pair, and the live and neutral wires connected to the other power receptacles are connected to the line connection pair, is an all-too-common occurrence.
- most GFCIs are unable to detect a ground fault at the GFCI receptacle connection pair since the current transformer is not positioned between the load connection pair and the receptacle connection pair, and thus cannot detect the resulting difference in current in the live and neutral current paths at that point.
- AFCIs arc fault circuit interrupters
- FIG. 1 is a block diagram of an example electrical safety device employing miswiring detection
- FIG. 2A is a block diagram of an example GFCI that is wired correctly and is not coupled with a load
- FIG. 2B is a block diagram of the example GFCI of FIG. 2A that is miswired and is not coupled with a load;
- FIG. 2C is a block diagram of the example GFCI of FIG. 2A that is wired correctly and is coupled with a load;
- FIG. 2D is a block diagram of the example GFCI of FIG. 2A that is miswired and is coupled with a load;
- FIG. 3 is an example switch circuit employable as a selectable low-ohmic path in the GFCI of FIGS. 2A through 2D ;
- FIG. 4 is an example selectable load employable as the selectable load in the GFCI of FIGS. 2A through 2D ;
- FIG. 5 is a flow diagram of an example method of detecting a miswiring of an electrical safety device.
- FIG. 1 is a block diagram of an example electrical safety device 100 employing miswire detection.
- the electrical safety device 100 may be any device configured to protect people or property in the event of some detected problem or anomaly in the electrical circuits or devices to which the electrical safety device 100 is connected or coupled.
- the electrical safety device 100 may be a ground fault circuit interrupter (GFCI).
- GFCI ground fault circuit interrupter
- AFCIs arc fault circuit interrupters
- SPDs surge protection devices
- TVSSes transient voltage surge suppressors
- combination devices such as, for example, combined GFCI/AFCI devices.
- the electrical safety device 100 is configured to detect a miswiring of the electrical safety device 100 to the electrical circuit in which it is installed. For example, in many of the embodiments described herein, the electrical safety device 100 is configured to determine if the line and load connections of the electrical safety device 100 are miswired or cross-wired, which may prevent detection of one or more circuit problems that the electrical safety device 100 was intended to detect and/or mitigate.
- the electrical safety device 100 may provide a line connection pair 120 , 122 including a line “hot” (or “live”) connection 120 and a line neutral connection 122 , and also provide a load connection pair 130 , 132 including a load hot (or live) connection 130 and a load neutral connection 132 .
- the line connection pair 120 , 122 may be connected directly to a circuit breaker panel or similar power distribution point, while the load connection pair 130 , 132 may be coupled to one or more power receptacles into which devices may be plugged to access electrical power.
- each of the live or hot connections 120 , 130 may carry an alternating current (AC) supply voltage that provides the electrical power to the devices consuming the power, while each of the neutral connections 122 , 132 may carry the return current from the devices back to the supplier of the power, such as the circuit breaker panel.
- the electrical safety device 100 may provide a receptacle connection pair 140 , 142 of a receptacle hot or live connection 140 and a receptacle neutral connection 142 so that one or more devices may access the electrical power directly from the electrical safety device 100 operating as a power receptacle.
- the electrical safety device 100 may be installed in a location that is not readily accessible as a power receptacle, such as in a circuit breaker panel, and thus may not provide the receptacle connection pair 140 , 142 .
- the electrical safety device 100 may also provide a ground connection in conjunction with each of the line connection pair 120 , 122 , the load connection pair 130 , 132 , and the receptacle connection pair 140 , 142 , which may be coupled to a conductive chassis and/or other portions of the devices accessing power via the electrical safety device 100 or other power receptacles connected thereto.
- the ground connections are not discussed further below to simplify and focus the following discussion.
- the electrical safety device 100 may include a differential current detector 102 , a control circuit 104 , a selectable low-ohmic or low-resistance conducting path 106 , and possibly a selectable load 108 .
- the electrical safety device 100 may include other components, such as one or more resistors, capacitors, inductors, silicon-controlled rectifiers (SCRs), transistors, input buttons, output components (e.g., one or more light-emitting diodes (LEDs), sound generation devices, and/or the like), and/or so on to perform various functions other than miswire detection, but are not explicitly depicted in FIG. 1 .
- the differential current detector 102 may be configured to detect a difference in electrical current being carried by a live or hot current path (such as the path between the line live connection 120 and the load live connection 130 ) and a neutral current path (such as the path between the line neutral connection 122 and the load neutral connection 132 ).
- a significant difference between the electrical currents carried by the live current path and the neutral current path may be interpreted as an undesirable or dangerous redirecting of current outside of the power distribution system and the electrical devices being supplied with the power.
- the differential current detector 102 may be employed to perform a standard operation associated with the electrical safety device 100 , such as ground fault detection, in addition to miswire detection, while the differential current detector 102 may be employed specifically for miswire detection in other examples.
- the differential current detector 102 may include a current transformer.
- the selectable low-ohmic path 106 may be configured to provide, when selected or activated, an additional current path coupling the line neutral connection 122 and the load neutral connection 132 while circumventing the differential current detector 102 to carry at least a portion of the current that otherwise would be carried over the neutral current path.
- the selectable low-ohmic path 106 may include a low-ohmic switch component that is selectable by way of a control signal sourced by the control circuit 104 .
- the selectable low-ohmic path 106 may be configured instead to provide an additional current path coupling the line live connection 120 and the load live connection 130 , as indicated in FIG. 1 .
- the control circuit 104 may be configured detect the difference in current (if any) over the live current path and the neutral current path via the differential current detector 102 .
- the control circuit 104 may select or activate the low-ohmic path 106 , and during the time that the low-ohmic path 106 is selected or activated, may detect whether a difference in currents carried over the live current path and the neutral current path exists or exceeds some threshold value. As is described in greater detail below with respect to the embodiments of FIGS.
- the absence of a difference in current may be indicative of a miswire condition, in which the AC supply voltage is applied across the load live connection 130 and the load neutral connection 132 , instead of the line live connection 120 and the line neutral connection 122 .
- a load such as an electrical device that consumes power
- the control circuit 104 may detect a polarity of the difference in currents carried over the live current path and the neutral current path and determine whether the electrical safety device 100 has been miswired based on that polarity.
- control circuit 104 may interrupt or disconnect the power of the AC power supply from the one or more loads that may be coupled to the electrical safety device 100 , such as in the manner normally done when other types of circuit problems, such as ground faults or arc faults, are detected.
- the control circuit 104 may activate a silicon-controlled rectifier (SCR) that energizes a solenoid to open one or more switches in the live current path and/or the neutral current path (not explicitly shown in FIG. 1 ), thus facilitating the disconnection.
- SCR silicon-controlled rectifier
- control circuit 104 in response to detecting the miswire condition, may employ an audio generation device (e.g., a speaker) to provide an audio indication of the condition, a light generation device (e.g., a light-emitting diode (LED)) to provide a visual indication of the condition, and/or a communication interface to provide a message notification over a communication network of the condition.
- an audio generation device e.g., a speaker
- a light generation device e.g., a light-emitting diode (LED)
- a communication interface to provide a message notification over a communication network of the condition.
- a load may be applied internally to the electrical safety device 100 to compensate for the lack of a load applied externally to the electrical safety device 100 , typically by way of the load connection pair 130 , 132 or the receptacle connection pair 140 , 142 .
- the control circuit 104 may draw enough current from the AC power supply voltage applied to the electrical safety device 100 , such as, for example, by way of an alternating-current-to-direct-current (AC-to-DC) converter (not explicitly shown in FIG. 1 ) located on the load side of the differential current detector 102 to serve as such a load.
- AC-to-DC alternating-current-to-direct-current
- the electrical safety device 100 may include a selectable load 108 located on the load side of the differential current detector 102 and controlled by the control circuit 104 , as shown in FIG. 1 , such that the control circuit 104 may apply the selectable load 108 across a point on the live current path and a point on the neutral current path.
- the control circuit 104 may employ the same control signal to select or activate both the selectable low-ohmic path 106 and the selectable load 108 to perform miswire detection.
- control circuit 104 may include, or be coupled with, one or more analog components (e.g., resistors, capacitors, inductors, and/or the like) to detect and/or control the various components described above. Also, the control circuit 104 may include, or be coupled with, one or more digital components (e.g., logic gates, counter integrated circuits (ICs), data latches and/or buffers, and so on) to perform one of more of the tasks with which the control circuit 104 is tasked. In some embodiments, the control circuit 104 may include a microcontroller or other algorithmic processor that may execute instructions stored in a data memory to perform one or more tasks or operations of the control circuit 104 described herein.
- analog components e.g., resistors, capacitors, inductors, and/or the like
- digital components e.g., logic gates, counter integrated circuits (ICs), data latches and/or buffers, and so on
- the control circuit 104 may include a microcontroller or other algorithmic processor that may
- FIGS. 2A through 2D are block diagrams of an example GFCI 200 in various states of correct and incorrect connection with an AC power supply 250 and a load 260 .
- the AC power supply 250 may be 110 volts AC (VAC), although other AC voltages may be provided by the AC power supply 250 in other embodiments.
- the GFCI 200 may include a current transformer (CT) 202 serving as the differential current detector 102 of FIG. 1 , a switch 206 operating as the low-ohmic path 106 of FIG. 1 , a control circuit 204 operating in a manner similar to that of the control circuit 104 of FIG.
- CT current transformer
- the switch 206 may instead couple the line live connection 120 to the load live connection 130 while circumventing the current transformer 202 , as described above in conjunction with the selectable low-ohmic path 106 of FIG. 1 , in other embodiments.
- the current transformer 202 includes a magnetic core, through which a line current path coupling the line live connection 120 to the load live connection 130 and a neutral current path coupling the line neutral connection 122 and the load neutral connection 132 are routed to serve collectively as a primary circuit for the current transformer 202 .
- the secondary circuit of the current transformer 202 may be in the form of a conductor wrapped a number of turns about the core and coupled to the control circuit 204 .
- the difference in currents carried over the live current path and the neutral current path creates a magnetic flux in the core, which in turn induces a current in the secondary circuit, with the number of turns of the wrapping conductor determining the amount of current carried in the secondary circuit, thus providing an indication of the difference in currents carried over the line current path and the load current path to the control circuit 204 as a sense signal.
- the GFCI 200 may include a user-operable reset button 210 coupled to a set of switches 212 to reconnect the load connection pair 130 , 132 and the receptacle connection pair 140 , 142 to the line connection pair 120 , 122 to allow current to flow through the GFCI 200 after a ground fault or a miswire configuration has been detected.
- the GFCI 200 may also include a test button (not depicted in FIGS. 2A through 2D ) that forces the switches 212 into an open state as if a circuit problem had been detected.
- FIG. 2A is a block diagram of the GFCI 200 being wired correctly to the AC supply 250 and not being coupled with a load. More specifically, the AC supply 250 is coupled to the line connection pair 120 , 122 , and nothing is coupled to the load connection pair 130 , 132 or the receptacle connection pair 140 , 142 .
- the control circuit 204 has selected or activated the switch 206 (as well as possibly the selectable load 208 )
- some of the current normally carried on the return current path is carried through the switch 206 , resulting in a current I h on the live current path, a current I g through the switch 206 , and a current I h ⁇ I g on the return current path.
- the overall current through the magnetic core of the current transformer 202 is the difference between the two currents, or I g .
- the control circuit 204 having detected a difference current, or having detected a difference current above some threshold value by way of a comparison circuit, may conclude that the GFCI 200 is wired correctly and may thus allow the GFCI to couple the AC supply 250 to the load connection pair 130 , 132 and the receptacle connection pair 140 , 142 .
- control circuit 204 may monitor the difference current and open one or more of the switches 212 in response to a detected difference current that exceeds some threshold while a load is coupled to either the load connection pair 130 , 132 and/or the receptacle connection pair 140 , 142 , thus indicating a ground fault condition.
- FIG. 2B is a block diagram of the GFCI 200 while the GFCI 200 is miswired to the AC supply 250 and is not coupled with a load. More specifically, the AC supply 250 is coupled to the load connection pair 130 , 132 by mistake. In this case, if a load is subsequently coupled to the line connection pair 120 , 122 , under normal ground fault detection operations of the GFCI 200 (e.g., when the switch 206 is open), the control circuit 204 will still be able to detect a ground fault at the line connection pair 120 , 122 , as any current that flows between the AC supply 250 and the load at the line connection pair 120 , 122 will still be routed through the current transformer 202 , so that any difference in currents carried over the live current path and the neutral current path will be detectable at the control circuit 204 .
- the control circuit 204 will still be able to detect a ground fault at the line connection pair 120 , 122 , as any current that flows between the AC supply 250 and the load at the line connection pair
- the control circuit 204 may detect such a miswired configuration by way of the switch 206 while the line connection pair 120 , 122 remains unconnected. More specifically, when the control circuit 204 activates or closes the switch 206 (and possibly activates the selectable load 208 , if present), no current will be available to be directed through the switch 206 and thus to be circumvented around the current transformer 202 , resulting in a current I g through the switch 206 of substantially zero, resulting in a differential current of substantially zero through the current transformer 202 regardless of whether a load is coupled across the receptacle connection pair 140 , 142 .
- the control circuit 204 may be configured to interpret this lack of differential current as a miswiring of the GFCI 200 , and to open at least one of the switches 212 to the prevent use of the GFCI 200 while the miswire condition persists.
- the detection of a substantially zero differential current may be sufficient to detect a miswire configuration, such as during power-up of the GFCI 200 via the AC supply 250 .
- a load may be applied incorrectly to the line connection pair 120 , 122
- consideration in the control circuit 204 of the polarity of any differential current detected may allow repeated or periodic testing of a miswire configuration after power-up.
- periodic miswire testing may be performed once every 15 minutes, but other longer or shorter time periods may be employed in other implementations.
- the miswire detection operations may be initiated in response to a user activating the test button mentioned above.
- FIG. 2C is a block diagram of the example GFCI 200 in an environment in which the AC supply 250 is wired correctly to the line connection pair 120 , 122 while one or more loads are wired correctly to the GFCI 200 via the load connection pair 130 , 132 and/or the receptacle connection pair 140 , 142 .
- FIG. 2D is a block diagram of the GFCI 200 that is miswired (e.g., the AC supply 250 is connected to the load connection pair 130 , 132 ) and the load 260 is connected to the line connection pair 120 , 122 .
- an additional load may or may not be connected to the receptacle connection pair 140 , 142 .
- the control circuit 204 may detect not only whether the differential current I s exists or exceeds some threshold, but may also determine the polarity of the differential current I s to determine whether the AC supply 250 is coupled to the line connection pair 120 , 122 or the load connection pair 130 , 132 .
- control circuit 204 may include a zero-cross-detect (ZCD) circuit (not explicitly depicted in FIG. 2D ) that indicates when the positive or negative voltage portion of each cycle of the AC supply 250 voltage is occurring. Based on the information from the ZCD circuit and the detected differential current, including its polarity (e.g., a negative or positive current), the control circuit 204 may determine whether the AC supply 250 is connected correctly to the GFCI 200 (e.g., to the line connection pair 120 , 122 ).
- ZCD zero-cross-detect
- control circuit 204 may determine that the AC supply 250 is miswired (e.g., connected to the load connection pair 130 , 132 ).
- the control circuit 204 may then determine that a miswire condition has been detected, and then open one or more of the switches 212 accordingly.
- control circuit 204 may activate or close the switch 206 , as well as the selectable load 208 , during a particular portion of the voltage cycle of the AC supply 250 , such as when the voltage is only positive or only negative.
- control circuit 204 may dynamically alter the amount of time the switch 206 is closed and the selectable load 208 is selected based on the detected differential current I s .
- the control circuit 204 may allow the switch 206 closed (and possibly the selectable load 208 to remain applied or selected) until the detected differential current I s attains the threshold at which the control circuit 204 determines that a miswire configuration has been detected, or some higher threshold level.
- the detected differential current I s may attain the threshold level more quickly than in the case of a low load current (e.g., a high resistance load), and thus the switch 206 may be closed for a relatively shorter time period. Further, in the case of the detected differential current I s not attaining the threshold, the control circuit 204 may await until the ZCD circuit determines that the current (positive or negative) half-cycle of the voltage of the AC supply 250 is over before opening the switch 206 , as well as deselecting the selectable load 208 .
- Operating the switch 206 , and possibly the selectable load 208 , in such a manner may help buildup of excessive current due to the inductance of the current transformer 202 that may otherwise occur if the switch 206 were always closed during the entire half-cycle of the AC supply 250 voltage. This excessive current may lead either to nuisance tripping of the GFCI 200 when an actual ground fault condition has not been encountered, or to a delayed response of the GFCI 200 in the presence of an actual ground fault event.
- FIG. 3 is an example circuit of a switch 206 employable as a selectable low-ohmic path in the GFCI 200 .
- a low-ohmic metal-oxide-semiconductor field-effect transistor may be employed as a transistor Q 1 to facilitate the switching functionality.
- MOSFET metal-oxide-semiconductor field-effect transistor
- An example of such a MOSFET is the NTMFS4935NT1G n-channel Power MOSFET by ON Semiconductor® with an “on” drain-to-source resistance of 3.2 milliohms (m ⁇ ) and a drain-to-source breakdown voltage of 30 volts (V).
- the switch 206 may also include a resistor R 1 of an appropriate value to apply at least a gate-to-source threshold voltage to turn on the transistor Q 1 .
- the resistor R 1 may have a value of 50 ⁇ , although other values may be employed in other implementations.
- the switch 206 may also include a rectifier D 1 , such as an MRA4007 by ON Semiconductor® in one example, driving the gate of the transistor Q 1 via a signal from the control circuit 204 , which may serve to protect the control circuit 204 from potentially damaging current from the switch 206 .
- a rectifier D 1 such as an MRA4007 by ON Semiconductor® in one example, driving the gate of the transistor Q 1 via a signal from the control circuit 204 , which may serve to protect the control circuit 204 from potentially damaging current from the switch 206 .
- a rectifier D 1 such as an MRA4007 by ON Semiconductor® in one example
- FIG. 4 is an example selectable load 208 employable in the GFCI 200 .
- a control signal from the control circuit 204 may be used to turn on a transistor Q 2 using a resistor R 2 to generate a positive bias voltage across the base-to-emitter junction of the transistor Q 2 to turn on the transistor Q 2 .
- the transistor Q 2 may be a MMBT6517LT1-D high-voltage NPN bipolar-junction transistor (BJT) by ON Semiconductor®, although other transistors may be employed as the transistor Q 2 in other embodiments.
- BJT NPN bipolar-junction transistor
- a resistor R 3 may provide the desired amount of resistance to be used as the load to be applied across the live and neutral current paths. Further, diodes D 2 and/or D 3 may be utilized to allow current to flow only from collector to emitter of the transistor Q 1 , while another diode D 4 may help protect the transistor Q 2 against large negative voltages at the output of transistor Q 1 .
- the selectable load 208 is intended to be applied as a load during positive half-cycles of the voltage of the AC supply 250 . However, many other configurations and components other than that shown in FIG. 4 may be employed for the selectable load 208 in other embodiments, such as those intended to operate during the negative half-cycle of the AC supply 250 voltage.
- FIG. 5 is a flow diagram of an example method 500 of detecting a miswiring of an electrical safety device, such as by way of the electrical safety device 100 of FIG. 1 or the GFCI 200 of FIGS. 2A through 2D .
- an electrical safety device such as by way of the electrical safety device 100 of FIG. 1 or the GFCI 200 of FIGS. 2A through 2D .
- other systems or devices not specifically described herein may perform the method 500 in other embodiments.
- a control circuit in response to power-up (operation 502 ) of the GFCI 200 due to application of the AC supply 250 , a control circuit (e.g., the control circuit 104 of FIG. 1 ) may activate or close a low-ohmic path (e.g., the low-ohmic path 106 around the differential current detector 102 ) (operation 504 ). To ensure enough load current is provided, the control circuit may also select a selectable load (e.g., the selectable load 108 of FIG. 1 ) to be applied across points of the live and neutral current paths of the electrical safety device.
- a selectable load e.g., the selectable load 108 of FIG. 1
- the control circuit may determine whether a differential current routed through a differential current detector (e.g., the differential current detector 102 of FIG. 1 ) exceeds some particular threshold (operation 506 ), such as, for example, 40 milliamps (mA). If the threshold is not exceeded, the control circuit may determine that a miswire condition has been detected, and open one or more of the live and neutral current paths to the load and/or receptacle connections (e.g., the load connection pair 130 , 132 and/or the receptacle connection pair 140 , 142 of FIG. 1 ) of the electrical safety device (operation 510 ) and cease operation (operation 512 ) until the miswire condition has been remedied.
- a differential current routed through a differential current detector e.g., the differential current detector 102 of FIG. 1
- some particular threshold such as, for example, 40 milliamps (mA). If the threshold is not exceeded, the control circuit may determine that a miswire condition has been detected, and open one or more of
- the control circuit may determine whether the detected differential current has a polarity corresponding to a correctly-wired AC supply (operation 508 ). If so, the control circuit may deactivate the low-ohmic path (as well as the selectable load) (operation 514 ) and wait for some predetermined period of time (operation 516 ) before performing another miswire detection operation. If, instead, the detected differential current has a polarity corresponding to an incorrectly wired AC supply (operation 508 ), the control circuit may open one or more of the current paths to the load and/or receptacle connections (operation 510 ) and cease further miswire detection operations (operation 512 ) until the electrical safety device is wired correctly.
- While the operations 502 - 516 are depicted as operations performed in a particular sequence, at least some of the operations 502 - 516 of FIG. 5 may be performed in other orders of execution, including in a parallel, overlapping, or concurrent manner.
- the threshold detection operation (operation 506 ) and the polarity determination operation (operation 508 ) may be performed simultaneously or in a different order from that indicated in FIG. 5 .
- the electrical safety device 100 is a GFCI, such as the GFCI 200 of FIGS. 2A through 2D
- GFCI GFCI 200 of FIGS. 2A through 2D
- employment of various aspects of the embodiments described herein may adhere to, and possibly surpass, the demands of the 2015 revisions of the Underwriters Laboratories (UL®) standard UL943 for GFCIs that mandate auto-monitoring or self-test functionality of its ground fault detection capabilities, as well as line-load miswire detection, such as that described above.
- UL® Underwriters Laboratories
- the term “or” may be construed in either an inclusive or exclusive sense. Moreover, plural instances may be provided for resources, operations, or structures described herein as a single instance. Additionally, boundaries between various resources and operations may be arbitrary, and particular operations are illustrated in a context of specific illustrative configurations. In general, structures and functionality presented as separate resources in the example configurations may be implemented as a combined structure or resource. Similarly, structures and functionality presented as a single resource may be implemented as separate resources.
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Emergency Protection Circuit Devices (AREA)
- Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)
Abstract
Description
Claims (18)
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
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US14/850,271 US10141734B2 (en) | 2014-10-26 | 2015-09-10 | Electrical safety device miswire detection |
CN201520797205.7U CN206712459U (en) | 2014-10-26 | 2015-10-15 | Electric safety device and the control circuit for electric safety device |
EP15191298.7A EP3012853B1 (en) | 2014-10-26 | 2015-10-23 | Electrical safety device miswire detection |
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US201462068743P | 2014-10-26 | 2014-10-26 | |
US14/850,271 US10141734B2 (en) | 2014-10-26 | 2015-09-10 | Electrical safety device miswire detection |
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US20160118785A1 US20160118785A1 (en) | 2016-04-28 |
US10141734B2 true US10141734B2 (en) | 2018-11-27 |
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TWI784321B (en) * | 2020-03-19 | 2022-11-21 | 奇景光電股份有限公司 | Method for performing hybrid over-current protection detection in a display module, and associated timing controller |
Families Citing this family (2)
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US10141734B2 (en) | 2014-10-26 | 2018-11-27 | Semiconductor Components Industries, Llc | Electrical safety device miswire detection |
US10958062B2 (en) * | 2018-11-13 | 2021-03-23 | Rockwell Automation Technologies, Inc. | Systems and methods for dynamically switching a load of a current transformer circuit |
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Also Published As
Publication number | Publication date |
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EP3012853B1 (en) | 2019-06-05 |
CN206712459U (en) | 2017-12-05 |
EP3012853A1 (en) | 2016-04-27 |
US20160118785A1 (en) | 2016-04-28 |
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